A semiconductor laser is usually used as a light source for a pickup device for recoding and reproducing information on and from a recording medium such as a DVD. The light beam emitted from the semiconductor laser has an elliptical shaped cross section since the beam is emitted from the end surface of a thin activation layer. When the light beam is shaped into a circular beam by using a beam shaping element, and is then used, efficiency of the light beam can be raised, whereby the accuracy of recording and reproducing can be improved. Particularly, such a beam shaping element is of great importance when used in a pickup device using a blue semiconductor laser as a light source since the blue semiconductor laser tends to have insufficient intensity of the emitted beam.
As the beam shaping element for shaping the cross section of a light beam emitted from a semiconductor laser, known is a beam shaping element (lens) which has a cylindrical surface with a curvature only in the direction the shorter axis of the cross section of the beam (see Patent Document 1, for example).
As a manufacturing method of an optical element such as the beam shaping element, a pressure-mold method using a metal molding die is known. In particular, a method in which an optical element is directly manufactured by pressure-molding a molten glass drop dispensed in a metal molding die is gathering attentions and is being investigated because very high production efficiency is expected in principle (see Patent Documents 2 and 3, for example).
High precision in positioning with respect to a light source is required when the beam shaping element is assembled into an optical system. Therefore, it is proposed in Patent Document 2 that an optical element is molded, in a square hole in a member having the square hole, to form a side molded-surface which is to be used as a reference surface when assembling. In Patent Document 3, proposed is a method where a method in which the temperature of a member, of a molding die, for forming a side molded-surface is set higher than the other members so that breaking and cracking are prevented, whereby an optical element having a positioning reference surface is stably manufactured.    Patent Document 1: Japanese Unexamined Laid-open Patent Application Publication No. 2002-208159    Patent Document 2: Japanese Unexamined Laid-open Patent Application Publication No. 2006-290692    Patent Document 3: Japanese Unexamined Laid-open Patent Application Publication No. 2004-339039